1. Field of the Invention
Aspects of the present invention relate to the cutting of semi-rigid coax cable on a computer numerical control (cnc) cable bending machine. More particularly, aspects of the present invention relates to the length of material remaining between the last formed bend and the adjacent end of the cable after the saw has severed the formed part from a long length of straight cable.
2. Description of the Related Art
Semi-rigid coax cable (cable) is used to transmit electrical signals. Having the ability to cut the cable accurately is important for the quality of the transmitted signal to remain high. For decades the cutting process of a bent profile has been accomplished by either a stand alone powered bench saw or a powered saw integrated into a cnc cable bending machine. The saw on a cable bending machine is mounted such that a fixed distance exists between the saw blade (cutting plane) and the center of a bend die. This distance is often attempted to be as short as possible. However, there is a minimum distance permissible before the saw blade starts to cut into the bend tooling. This has been a limitation of this type of cutting process for decades. This distance is often referred to in the cable bending industry as the minimum last leg length. The minimum last leg length therefore defines how short the last leg can be processed on a specific cnc bending machine. Thus, the last leg length is the length of the straight portion of the cable from the end of the cable to the bend that is formed therein.
During the normal course of bending coax cable, a cnc bending machine often accepts a long length of semi-rigid coax cable to process. From this long length of cable, several individual parts can be fabricated provided that the cnc bending machine has an integrated saw as part of the function of the overall system. When a saw exists within the system, a typical user of the bending machine will program the machine to make one or more specific bends within a cable. After the last bend has been processed, the controller on the machine may instruct the user to cut the cable. Normally the system can move the cable forward after the last bend to make the cut, but the system has been unable to pull the cable backwards to make a cut because the last bend formed in the cable is wrapped (hooked) around the bend tooling.
Some cables are designed with a last leg length less than the minimum allowable last leg length as specified by the manufacturer of the cable bending machine. When this happens, the user of the bending equipment who is fabricating the bent coax cable must perform a secondary trim operation to further remove material from the cable's end to meet the required last leg length.
Over the years, Pines Technology (Westlake, Ohio) has built cnc cable bending equipment with an integrated saw to cut semi-rigid coax cable on a cnc bending machine. Their equipment, as described above, has a fixed distance from the plane of cut to the center of the bend die. This fixed distance determines the minimum last leg length that can be processed on the cable bender. It has never been considered obvious to backup and cut the cable because the last bend formed in the cable is wrapped (hooked) around the bend tooling.
Likewise, Winton Machine (Suwanee, Ga.) has built cnc cable bending equipment with an integrated saw to cut semi-rigid coax cable. Their equipment, as described above as well, has a fixed distance from the plane of cut to the center of the bend die. This fixed distance determines the minimum last leg length that can be processed without using a secondary cutting operation. It has never been considered obvious to backup and cut the cable because the last bend formed in the cable is wrapped (hooked) around the bend tooling. Backing up would have a tendency to unbend the cable and thus result in a non-conforming profile.
The hardship over the years when bending with an integrated cutting device has been to live with the minimum last leg length as specified by the machine tool builders and perform with a secondary trim operation as needed. The secondary trim operation adds to the cost of goods sold.
U.S. Pat. No. 8,234,772 assigned to Schleuniger does provide for cutting a flexible cable while offering a means to move the cable forward and backwards prior to cutting. However, Schleuniger does not provide a means for bending in the same apparatus. Also, Schleuinger makes use of a shear type cut and a shear type cut has been known to damage the ends of semi-rigid coax cable. It would not have been obvious to add a bending operation to this type of equipment because the apparatus of the cutting process would get in the way of bending the most simplistic profile.